React - counter

import React, { Component } from 'react';

class Counter extends Component {
    render() {
        const { counter } = this.props;
        return (
            <div className='counter'>
                <button
                    className='btn btn-primary'
                    onClick={() => this.props.onIncrement(counter)}
                >
                    Increment
                </button>
                <button
                    className='btn btn-secondary'
                    onClick={() => this.props.onDecrement(counter)}
                >
                    Decrement
                </button>
                <span className={this.getValueClass()}>
                    {this.formatCount()}
                </span>
            </div>
        );
    }

    formatCount = () => {
        const { value } = this.props.counter;
        return value === 0 ? 'zero' : value;
    };

    getValueClass = () => {
        const { value } = this.props.counter;
        let cssClass = 'badge badge-';
        cssClass += value === 0 ? 'warning' : 'dark';
        return cssClass;
    };
}

export default Counter;